Before you decide to purchase an electronic keyboard, be sure you at least know the basic differences between an acoustic piano, a digital piano vs a digital stage piano, an electronic keyboard and a MIDI controller keyboard.
1. Acoustic pianos
Acoustic pianos are traditional pianos with hammers and strings producing the booming, resonant sounds. They are large, not portable and come with a hefty price tag. They will require occasional tuning. These are suitable for those who love the sound of the piano, are already probably taking offline piano lessons (and thus are sure of their dedication towards mastering it), and have the budget and room space.
2. Digital pianos
Digital pianos are a cheaper alternative to acoustic pianos; they do not have hammers or strings and instead attempt to mimic the sound of acoustic pianos electronically. They usually have “weighted keys” to (attempt to) emulate the feel of traditional piano keys.
Casio AP420, a digital piano in the mid-price range (around $1100+)
Yamaha YDPV240, a digital piano in the higher-end price range (around $2000+)
Some digital pianos also offer a small range of other instrumental sounds (e.g. strings, harpsichord). They are smaller and thus take up less room than traditional pianos and, as another upside, do not require any tuning. These digital pianos are suitable for those who love the acoustic piano’s sound but are budget or space-constrained.
3. Digital stage pianos (or simply “stage pianos”)
These are a subset of digital pianos. While most digital pianos attempt to emulate the look, feel and sound of the traditional acoustic piano, digital stage pianos only attempt to mimic the feel and sound. They can be highly portable as they do not resemble acoustic pianos.
Casio PX-130 digital stage piano (around $500+)
A distinguishing feature of digital stage pianos is that most (though not all) do NOT come with inbuilt speakers. Instead, since they are mainly meant for use on stage, external speakers or amplifiers are expected to be used. Digital stage pianos typically come with the full set of 88 black and white keys, like traditional acoustic pianos.
4. Electronic keyboards
Electronic (also called “digital” or “portable”) keyboards are highly portable and are usually cheaper than digital pianos. Keyboards usually offer a wider range of other instrumental sounds (e.g. flute, drums) than digital pianos. In addition, they often have an “auto-accompaniment” feature, where chords (a chord is essentially a specific group of notes or keys played at the same time) are played by pressing a single key.
As a drawback, an electronic keyboard’s actual piano tone is usually considered of lower quality than a digital piano, and usually lack the “feel” of an acoustic piano. The main distinction between digital pianos and keyboards (apart from portability) is that the latter typically does not have weighted keys (some do have weighted keys, but they usually do not come as close as a digital piano does in emulating the weight/feel of an acoustic piano’s keys).
Yamaha YPG-235 (76 keys) is an example of a portable electronic keyboard (around $350+) with weighted keys
Electronic keyboards can be considered a jack of all trades instrument. They are highly suitable for complete beginners to musical instruments, hobbyist or “casual” musicians, professional musicians who love the flexible, all-in-one aspect of the instrument, and even those who might be interested in graduating to the acoustic piano in the future, but wish to test the waters before plunging in.
5. MIDI controller keyboard
A MIDI (Musical Instrument Digital Interface, a standard interface for musical instruments to communicate with one another digitally) controller keyboard is an electronic keyboard that typically does not produce sound on its own. Instead, the keyboard is connected via cable to some other audio-enabled MIDI-compatible device such as your computer or a device known as a sound module (synthesizer). When you press a key on the MIDI controller keyboard, a MIDI signal (known as an event or message) is generated and sent to the other device, which then generates the appropriate sound (or performs some other function).
The M-Audio Oxygen 49-Key is an example of a MIDI controller keyboard (about $100+)
Such keyboards can be a decent alternative to the standard electronic keyboard if you are on a very tight budget, as they are typically cheaper. Using such keyboards does require some additional effort and technical know-how (e.g. how to use the sequencer software).
Note that nearly all the standard electronic keyboards that have on-board sounds (i.e. they can generate sounds on their own) are also MIDI-compatible. Thus, they can be used as a MIDI controller when connected to another MIDI device to generate sounds.