There are lots of different types of therapy, and they all tend to work best if you go in with specific goals so that your therapist can tailor their approach (e.g. I want to change a behaviour pattern, or improve my self esteem, or manage my panic attacks etc etc). A good therapist has the expert knowledge to help you identify where your problems are coming from and/or recommend strategies to help.

Most of the therapy I've done is CBT which is pretty popular, it's based on behavioural psychology and is essentially about recognising and responding to your unhealthy thinking/behaviour. Acceptance and commitment and dialectic therapies are more mindfulness based. Or if you're in the US (possibly elsewhere but I've never done it in Aus) psychodynamic/psychoanalytic therapy is a bit more popular, that's the Freud type stuff where you delve into your childhood more. Most good therapists will use a combination of approaches but picking one that aligns with your goals is important.

I disagree with the idea that talking to a therapist is like venting to a friend, they are very different relationships. If I've done all the talking in a therapy session I feel seriously short-changed!