You can actually (kind of) make teams right now. You want to use tags to give the players, let's say, a BlueTeam or RedTeam tag. This will allow you to keep track of which team each player is on. If you want to display teams, you can add a scoreboard and have everyone with a BlueTeam tag a score of 1 and everyone with a RedTeam tag a score of 3. You can then use the 0 and 2 numbers to change the colour of the players on the scoreboard and write "Blue Team" and "Red Team" above the players.
The Meaning of Life, the Universe, and Everything.
There is a way to do this to a certain extent with /scoreboard.
First you would create one scoreboard for each team. For example: /scoreboard objectives add Blue dummy. Then /scoreboard objectives add Red dummy. When you join the blue team it would do /scoreboard players add @p Blue 1. Then whenever you make something that only the blue team could access, you would make in a command block /scoreboard players test @p Blue 1. Then the command which you want it to do would be in a conditional command block as an output of the first command block. Unfortunately, this doesn't prevent players on the same team from killing each other.