A pledge team is basically a full team built on the foundations of the various pledges. These pledges are Water, Grass and Fire pledges which are available only to starters. Of course, this has to be a doubles team.
When pledge moves are used alongside each other, they get useful effects. See the above links for the various effects they have. An example of this, in doubles (as far as I've seen), is the 1st gen starter core.
Venusaur @ Black Sludge
Ability: Chlorophyll
EVs: 252 HP / 252 SpA / 4 Spd
Modest Nature
IVs: 0 Atk / 2 Spd
- Sleep Powder
- Sludge Bomb
- Grass Pledge
- Protect
Blastoise @ Sitrus Berry
Ability: Torrent
EVs: 252 HP / 4 Def / 252 Sp.Def
Calm Nature
- Fake Out
- Yawn / Follow Me
- Water Pledge
- Protect
Charizard @ Charizardite Y
Ability: Blaze
EVs: 4 HP / 252 SpA / 252 Spd
Timid Nature
- Solar Beam
- Heat Wave
- Fire Pledge
- Protect
Hope I helped!