jump to label

[Efim Monyak]

Hi,

I have seen in the assembler sources jumps to numerical labels.
i.e.
1:
beq 1b
...
1:
beq 1b

or
beq 99f
99:

the as description says:
5.1 Labels
A label is written as a symbol immediately followed by a colon `:'. The 
symbol then represents the current value of the active location counter, 
and is, for example, a suitable instruction operand. You are warned if 
you use the same symbol to represent two different locations: the first 
definition overrides any other definitions.
[snip]

I don't found the description of this syntax, what does 'b' or 'f' mean?
Is this a specific label type?

Thanks