O.K. i don't know if i can explain it as you wish but...

When you do your program, you need to use some variable. Depending how you work you may need 3 different type of them

BIT
BYTE
WORD

Bit is only 2 conditions: 1 or 0 : usually to test bit or set test flag
BYTE : 256 condition or items
WORD : 65536 conditions or items

By using LED VAR BYTE, you are able to store/read 256 different items to it. BYTE = 8 bits

LED is the name of the variable BYTE is it's size.

Code:
TRISB = 0 'Set PORTB as output on all pins
LED VAR BYTE

start:
     FOR LED = 0 TO 255
          PORTB=LED ' send content of LED var to PORTB
          PAUSE 500 ' wait .5 sec
     NEXT B
     GOTO Start ' redo the loop
hope this help