A CD player reads digital data off discs and converts it to an analogue language which can be understood by an amplifier and speakers.
Theoretically  CD players with 24-bit digital to analog converters (DACs) will read every bit of data encoded on standard CDs, which are recorded at 16-bit resolution.

24-bit CD players read data very quickly usually at speeds of 192K and again theoretically pass on every bit of detail to an amplifier.

The better CD players have noise-free laser/transport mechanism which means the parts reading and spinning a CD should be noise-less. Typically single-disc players will be quieter than multi-disc CD players.
A well-featured CD player will playback music recorded on CD-R and erasable CD-RW blank discs. It will also play music recorded using MP3 or WMA files. Some will also playback the higher resolution SACD discs.

A player with a solid disc-.reading mechanism should sail through CDs that have the odd scuff or scratch. But don’t expect any CD player to read any CD that has been totally abused.

Though rare on budget to mid-priced models adjustable feet so you can level the player so that it’s horizontal to the surface it’s sitting on, are a desirable feature. Players that are level are working to their potential.