Basically, Apophis and Heru'ur were having a meeting in the Tobin system - which is full of mines that attack certain energy signatures (IE, weapons fire) and thus presumed to be neutral territory.
Heru'ur had earlier captured Teal'c at a meeting of rebel Jaffa on Chulak and had brought him along to give to Apophis as a gift to secure their new alliance against the other System Lords. But Raknor got talked around by Teal'c during his torture sessions, so when Heru'ur was supposed to ring Teal'c to Apophis' Cheops class mothership, all Apophis got was a dead minor Goa'uld.
Then a Tok'ra aboard Apophis' ship activated a signal which attracted one of the mines that SG-1 had just reprogrammed.
So Apophis never got Teal'c and then his ship starts rocking and thudding like it's been fired upon. So he powers up his ship's super-cannon and blows the ****ing crap out of Heru'ur's mothership. Then all the mines - having detected weapon's fire - start swarming all over Apophis and he has to use like 12 other (previously cloaked) motherships to keep the mines from getting to his ship so he can get away.
As for the ep-gaps:
The US shows the first half of the season, then breaks for new programs to air in September and picks back up in January/February with the second half of the season. All of which is on Sci-fi, IIRC.
In Canada, two different stations have the rights to SG-1 and Atlantis. So one station ignores the winter break or has a shortened break and world-premiere's Atlantis about 2 months before it airs in the US and a month before the UK. Then the other station picks up SG-1 about the same time as the US.
The UK does the same as the US, but has a shorter break than the US and a longer one that Canada's Atlantis break.
Use the spoiler tags please. -Fury