start here:
https://www.electro-tech-online.com/threads/pic-newcomers-please-read-upd-0xd1.15035/
That is mostly PIC (microchip's uC) related but can be applied to other manufacturers too
just like there is a bunch of car manufacturers making different car's there's bunch of companies making uC's. They all have same characteristics that make them uC's (cpu, ram, peripherals) but then again they are all different (type of cpu, amount of ram/rom, internal architecture - harvard or fon noyman, different peripherals - usart, ccp, adc, dac... different speed ...)
you can group them into families, each family have basic similarities (similar cpu and architecture, different speed and peripherals). Usually one family share
- sw dev tools (assemblers, compilers ..)
- hw dev tools (programmer, in circuit debugger, in circuit emulator ..)
example of families would be: pic16f, pic18f, dspic, attiny, msp430F4, msp430F2, msp430F1...
some programmers can programm only single chip, some can do whole family, some can do multiple families .. some are half there, for e.g. my old programmer could do any PIC that is 5V operated but none that is 3V or less ... the current one can do almost all PIC's ... I have another one that can do any uC from any MSP430* family ... etc etc ...
Necessary sw/hw depends on the uC. In 99.99% cases (depends on the manufacturer really), you will get free assembler and that's about it. On top of that you need a programmer so you can "burn" the binary into uC. That's all that you really need, but, asm programming is slow and incredibly hard to maintain so if you need any level of maintainability or feasibility, you go with higher level language, namely C. There are other possibilities like basic, pascal and some other "new" languages (like JAL, B# ..) but C is what is "common" today.
Evaluation board is usually a board that features uC + programmer (embedded or separate) + external hw (usually bunch of LED's and switches and maybe few analog inputs) that you can use to learn basics of specific uC family. For example pic16F family eval board is likely to have few led's, few switches, analog input, txt character display and rs232 port ... pic18F dev board will probably have USB port, maybe CAN or LIN external interface ... dsPIC will probably allow you to do some signal processing so graphics lcd with few analog inputs and oscilloscope like firmware ... etc etc etc ... Note that you do not have only uC general eval boards, there are specific boards, for example you have XBEE PRO eval board where uC is irrelevant, the think you are evaluating is the XBEE module .. etc .. check out the
mikroElektronika | Solutions for the embedded systems site, they have different dev boards + eval extensions for the dev board for different families of uC's, and also some universal boards that can be used for multiple families (even different brands) like: **broken link removed**
Do not get this as advert for mikroe, if you search this forum you will find me bitching about them a lot (theirs PIC dev tools, both hw and se are not compatible with microchip tools like MPLAB and that is BIG minus for them), but they do show excellent example of what dev/eval board is.
hope this helps, btw uC == micro controller