Tom explained that bass and baitfish are attracted to wood. Algae grows on it and plankton feed on that, and baitfish feed on both, and bass, , crappie and other species feed on the baitfish. That why fish are attracted to any stable surface like riprap where current is low and sun hits to allow photosynthesis.
That goes on all year long, so the ingredients for catching fish around wood are always there. In spring it's obvious why they might not be there much, active closer to spawning areas. In fall they are following baitfish that avoid traps like woods, moving to open water.
Lots of lakes have long ago given up the last standing wood, but if you have standing submerged trees it's a good idea to learn the seasonal situations. I'll talk a bit about winter. Whenever part of the trees stick up above the surface, birds often roost there all winter. Their droppings fertilize the water around the roost tree, so algae gets thicker around those trees than those completely under water. Look for roost snags.
It should be obvious the snags provide excellent shade in summer, but in winter they also provide dark ambush vantages for bass, the shade being deeper. As noted above any sunlight penetrating to the wood warms it and is retained a while, another attractor for a cold blooded bass.
Now lets bring in another fact do we can tie some things together. We know bass are lethargic, not willing to chase a meal down. They hide behind snags waiting for a hapless baitfish or panfish to get too close. Bream and crappie are there too, enjoying the bounty of a stand of snags. Whenever a prey fish is attacked it emits sounds and pheromones to alert their neighbors. Little fish dart suddenly in every direction, slamming into wood worrying too much about what might be behind them. They don't have the same lateral line feature bass have, so are more prone to bang into things.
Whenever fishing wood, ALWAYS bang your lure into wood, regardless of lure type. Bass see that as perfectly normal, and see it as an advantage. So bang and pause a second like a baitfish recovering from getting its snout smashed. Guide the bait, whether a spinnerbait, jig, crankbait, whatever, to hit as much wood as possible.
Winter is a time when most activity occurs around snags. A hot summer period is another peak period when all fish want to be shallow but need some shade. A less dramatic time is as Tom pointed out when females prepare for the spawn. The girls are both massaging egg sacks and leaving a scent trail for a male to locate them.
Right now through winter locate the tallest trees associated with steep drop offs. I head straight for 90' tall submerged wood on a slope that goes from 10' deep to 100' deep in about 100-150' of surface distance. For ya'll fishing on shallow lakes just look for wood on steep slopes even if that only involves 3' of elevation difference, or find a beaver hut, brush pile, or laydown.
Jim