list - Meaning of --> in swi-prolog -

i novice in ptolog. saw piece of code. want know meaning of parts of , how use it.

the code below:

matrixtconcat([]) --> []. matrix_tconcat([cs|css]) -->    row_rows_rest_(cs,css,mss),    matrix_tconcat(mss). 

first,what's meaning of -->

second,why matrixtconcat starts capital letter while matrix_tconcatstarts lower one? difference between them?

here piece of code:

rowrowsrest([],css,[]) -->    { emptylists(css) }. row_rows_rest_([x|xs],xss,[xs|mss]) -->    [x],    nonemptyrows_rest(xss,mss). 

what {and} in prolog used ,and how use it?