" 'til" is just an abbreviation of "until". There's no difference in meaning. I don't know if the spelling of " 'til" as "till" as a regional difference or a spelling mistake, but here it's always spelled with one 'l' and an apostrophe.

Whether or not you want to pronounce the whole word

Until and till are used to talk about the time when something stops.

the other answers are correct, there is no difference in meaning between the abbreviated version of Until and till. Till (when shortened) is also a homophone. A 'till' is also a word used in some places to mean 'cash register'. A till is also a Farm tool for creating cut lines in the soil.