Hogmanay is the Scots name for New Year's Eve. They have a lot of traditions associated with it - eg 'first footing' (crossing your neighbours' thresholds immediately after the bells, to wish them good luck). Some towns have very well known ceremonies, such as the Stonehaven fireball one, where about 45 men carry burning fireballs above their heads through the 'auld toon' (the old traditional part of the town), swinging them about as they walk.
As in most places now, at least in the UK, Hogmanay is also an excuse for many people to get blind drunk and cause trouble. There are big street parties in Edinburgh, Glasgow, etc, funded by the local councils, although they've cut back a lot in recent years. There are usually pop bands, and the whole thing is heavily policed to keep everything under control. There are fireworks at midnight. However, many older people will just have friends round for dinner and stay up to see the new year in. They would drink Scotch whisky and eat steak pie, clootie dumpling (a sort of boiled fruit cake thing), etc.
I am sorry to admit that I have absolutely no interest in Hogmanay (well, I'm not Scottish!) and am usually in bed before 11pm!
Rosemary