Apologies for such a simple question but I have just started to learn Turkish and I am confused about the difference in "siz" and "sen". Why are there two words for "you" and when are they used?

Thank you for any help

Simple: sen is used as singular (second person) and informal, siz is used as plural (second person) or as the polite way of 'you singular' (to strangers, elderly people etc.).

thank you Trudy I understand now. Its not clear in the Learn Turkish section.