'Set' can mean 'ready', so:

'Are you set? Then let's begin.'

'A set' can mean 'a collection'.

'This video is part of a set of English In A Minute videos.'

'Set' can also mean 'put in place'.

'I can set my glass on the table.'

We can also 'set a date' and this means 'to arrange a date', for example:

'We have set the date for our wedding. It's on the 1st of June'.

If we are 'set on something', we are strongly in favor of it, for example: 'I am set on getting married in June.'

And we can use 'set against' to say that we are 'strongly against something', for example:

'My parents are set against my wedding.'

Oh, no!