I am copying this from somewhere: Tolong is used when we ask someone to do something for you, whilst “silakan” is used when you offer something to someone.
For example: – Tolong buka pintu ini! (Please open this door.) You’re asking someone to open the door for you. – Silakan duduk. (Please sit down.) You’re offering someone to sit, but if they don’t want to sit, it’s up to them.