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:
- Adding friends (limited accounts can still create quick invite codes)
- Voting on Steam Reviews and Workshop items
- Participating in the Steam Market
- Trading Steam Community items (trading cards, booster packs, gems, etc.)
- Making your Steam profile visible to non-friends
- 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
- Creating public Steam guides
- 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
- Following/adding curators
- Posting hyperlinks in the Steam Community
- Adding a phone number from some countries
So, I assume you are able to do the above after spending five dollars.
According to this article by Valve, this is what a "premium" account gets over a "free" (officially called "limited account") one:
- Adding friends (limited accounts can still create quick invite codes)
- Voting on Steam Reviews and Workshop items
- Participating in the Steam Market
- Trading Steam Community items (trading cards, booster packs, gems, etc.)
- Making your Steam profile visible to non-friends
- 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
- Creating public Steam guides
- 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
- Following/adding curators
- Posting hyperlinks in the Steam Community
- Adding a phone number from some countries
