Spending more than $5 on Steam upgrades your account from a limited one to a premium one. I know there are a few benefits and privileges enjoyed by premium account holders, such as adding friends.
What other features do you gain access to as a paid member that limited members don’t get?
According to Steam’s help page:
Limited users are prevented from accessing several features on Steam,
including but not limited to:
- Sending friend and group invites
- Requesting access to groups
- Opening group chat
- Voting on Steam Reviews and Workshop items
- Participating in the Steam Market
- Trading Steam Community items (trading cards, booster packs, gems, etc.)
- Posting frequently in the Steam Discussions
- Gaining Steam Profile Levels (Locked to level 0) and Trading Cards
- Submitting content on the Steam Workshop
- Posting in an item’s Steam Workshop Discussions
- Accessing the Steam Web API
- Using browser and mobile chat
- Adding public artwork and screenshots
- Adding messages to trade offers
- Creating Steam groups
- Counting towards Steam group membership
So, I assume you are able to do the above after spending five dollars.