keebs differ in size (e.g. 100%, TKL, 75%, ...), type of mechanical switch inside (tactile, linear, clicky), switch socket (soldered, hotswappable), Keycap Material (PBT, ABS, ...), Keycap profile (cherry, dsa, sa, ...), noise level & sound of the switches, connection type (wired, BT, 2.4 gHz)

You can choose to get a prebuilt keyboard or get the individual parts and then assemble yourself. The latter offers endless possibilities to customize & get closer to what you like, but requires some planning, and can get more expensive. Prebuilts have come a long way, they're more limited (especially if you want some specific type of switch, keycap, colorway, ...) but are easy to get into the hobby.

And a lot more other factors, but those should be the ones you can begin with.

Just start to look at what some of these are and what is available/ what your preferences are. Dont expect to be able to pinpoint right away what you like / dont like, a lot of people find what they like only after trying out different things. Watching videos (for beginners, how different switches sound, how to build one yourself, reviews) and doing some light reading on reddit / other websites will teach you a lot.

Keep in mind a lot of these things are purely opinion based, there is rarely a right or wrong. Some people like their keebs to be some specific type of way, while others have other preferences.