Like his name says, TDM is like a duel with severals players and teams. In addition, TDM gets PowerUps, which is the main difference of gameplay compared to duel.

In TDM, a frag give 1 point the team, a suicide or a team kill remove 1 point.

TDM is harder to play and more tactical than duel. Weapons respawn is 30 seconds (instead of 5 or 15), then die is really penalizing. All the others items are standard.

TDM maps get at least one PU (Quad) and maximum 2 (BS or Invis). Their respawn time is standard (90 and 180 seconds).
Let's notice that most of the time, if PUs are not delayed, second PU (BS or Invis) respawns at the same time of Quad.
Beware that when the PU carrier is fragged, the PU is lost.

Most of the time, TDM is played with 8 players.

TDM is 20 minutes longs and an overtime of 5 mins is added until a team take the lead at the end of the given time.

Special note :
2v2 is a "submode" of TDM (to be right, this is a submode of 1v1, but 2v2 is closer to tdm). All the rules are the same but maps should be smaller. There are rarely more than a PU on these maps.
2v2 is 15 minutes long (OT=5minutes).
Weapon respawn is set to 10s.

The most played maps in TDM are :

Foolish Legacy (CPM21)
Inspired (CPM27)
Deep Inside (OSPDM5a)
Realm of Steel Rats (CPM4a)
Powahaus Redux (CPM18r)
Out of the Dark (CPM26)
Grim Dungeons(NODM18)
Get up, Stand up(AVRDM1B)

The most played maps in 2v2 are :

Solid (CPM29)
Ptolemy's Wrath (CPM25)
Iron Lung (CPM16)
Blood Run (ZT3DM1)
The Hot Place (PUKKA3DM1)
Patibuh's Lair (CPM15)
Shaft Area 22 (cpm17)
Fool's choice (XFDM2)