How does this x86 addressing mode work?

Question

Something like al will contain the address of esi + ecx + 1 ?

movb (%esi, %ecx, 1), %al

Answer 1

It loads the byte at memory address esi + ecx into al.

In general, in AT&T syntax,

(base, offset, multiplier)

refers to the datum located at memory address base + offset*multiplier.