I noticed you write YA, Jordygirl. Me too. I don't know which conference in particular you're considering, but if there's a regional SCBWI conference near you, I highly recommend going. I go to my regional SCBWI conferences, and they're a great way to connect with people in the industry as well as other writers.
There are a few different parts in a typical SCBWI conference (and this applies to the other conferences I've been to, as well):
Keynote Session - A noted author or publishing industry professional speaks to the entire group of conference attendees.
Breakout Sessions / Workshops - There's a schedule of various sessions, and you pick the ones that best fit your areas of interest. There's often a writing or revising activity, a partner activity, or a close reading of a published work.
Critique Sessions and/or Pitch Sessions - In a formal critique, you submit work beforehand (usually the first 20 pages of your manuscript), and one of the conference faculty members will read it, make notes, and then spend about 15 - 20 minutes in a scheduled session going over your work with you. I've found this to be extremely valuable. It'll cost you extra (maybe $35 or $40), but it's so worth it. And if you work with an agent or editor, you might get a request to send them more material.
I've never done a pitch session myself, but I was a timekeeper for them when I volunteered at a conference earlier this year, so I've heard a lot of them. Basically, you're given a set amount of time (between 5 and 10 minutes, usually) to give an oral version of your query letter to an agent or editor. This often starts out as just the author talking, but becomes a Q&A between author and agent/editor by the end. This can also result in a request for pages. My local SCBWI conferences don't have pitch sessions, but a lot of other conferences do.
Meals / Social Time - This is one of the best things about a conference. Eating, drinking, and talking with other serious writers? Fantastic. Get some business cards made beforehand and just be prepared to chat and network.
Most of the conferences I've been to have had a pretty even split between craft-related sessions / workshops (finding your voice, finding inspiration, working in a particular POV, creating dialogue that works, etc.) and business-related sessions (writing query letters, making connections with editors, managing your career, etc.). It's good to have that kind of balance, in my opinion.
As Madison said, definitely be prepared to be one of the youngest people there! I'm 28 (though look younger) and am usually one of the youngest people at the conferences I attend. I get a lot of "oh, I have a daughter about your age." I don't mind that, though.
Good luck with it!