I am considering getting a Boss RC-2 soon and I was watching some videos on the internet and I saw lots of people using it with the Boss FS-5U footswitch

i know what a footswitch does but what does it do when you use it with the RC-2?

is it essential??

It's not essential. I have the Boss RC-2 and I don't use a pedal with it. The pedal is used to change the tempo, I believe. Theres a youtube demonstartion on it that demonstrated the pedal + footswitch
WTLTL 2011