Sessions last approximately 45-50 minutes and typically occur on a weekly basis. Sessions are always booked on the hour, e.g. 9 am (not 9:30 am). Sessions are not a full hour, because clients are seen on the hour, every hour, and the therapist needs 10 minutes between clients to write the session note, and to prepare for the next client.
If you are in distress you can be seen more frequently as needed (e.g., twice a week), or if things are going more-or-less fine or if finances are an issue, you can be seen less often (e.g., every 2 weeks or once a month). However, a once-a-week format is most typical because it allows for enough time between the sessions for you to work on whatever was discussed in the session, but not so much time that the next session is spent updating the therapist on a lot of things that have happened between the sessions.