This isn't the place to learn all the details. You can read some of the pieces here, here, here or here. According to reports the trade is:
From Boston to Los Angeles: Adrian Gonzalez, Carl Crawford, Josh Beckett, Nick Punto, $12 million in cash
From Los Angeles to Boston: James Loney, Rubby de la Rosa, Jerry Sands, Ivan DeJesus and Allen Webster
Interesting to me is, unsurprisingly, the sheer amount of contracts changing hands. As noted by Jeff Euston:
Dodgers pre-trade - 2013: $135.5m, 2014: $76.6m, 2015: $48.5m, 2016: $46.9m, 2017: $47.5m.
Dodgers post-trade - 2013: $193.8m, 2014: $133.6m, 2015: $90m, 2016: $88.7m, 2017: $90m.
Red Sox pre-trade - 2013: $106.9m, 2014: $94.4m, 2015: $56m, 2016: $43.7m, 2017: $43.7m.
Red Sox post-trade - 2013: $45.6m, 2014: $34.4m, 2015: $12.8m, 2016: $2.5m, 2017: $0.
The last, and only, time a player with at least $100 million left in contracts was traded was Alex Rodriguez in 2004. Both Crawford and Gonzalez have over $100 million left owed. The Dodgers will have four players — Matt Kemp, Andre Ethier, Andrian Gonzalez and Carl Crawford — all with contracts that run through 2017, Ethier has a vesting option for 2018, Gonzalez is guaranteed through 2018 and Kemp is paid through 2019.
The Red Sox basically go from the luxury tax stratosphere to having almost no salary commitments overnight. The Red Sox will spend, so they could now hoover up much of the talent this winter. That also means that David Ortiz is probably a less likely get for the Mariners. The Red Sox will be pressed to acquiesce to Ortiz's demands now after gutting the team around him and potentially facing a fan backlash.