The 'EQU' simply means the name on the left is associated with the number on the right, it doesn't reserve or define memory at all. This means you can use it as a reference to a memory location or you can use it as a constant or even as part of a math calculation.
For example:
myvalue EQU 0x100
means wherever you use 'myvalue' in the program, 0x100 will be used in its place. So if you used the instruction 'mowvf myvalue' the content of W would be stored at location 0x100, if you used 'addlw myvalue' you would add 0x100 to W.
0x100 is defined as hexadecimal 100, it might be the same as plain 100 depending on the radix you have chosen. I think in MPLAB, it would be interpreted as 100 decimal by default but your assembler may be different.
Brian.