The space under a bed is usually the largest empty volume in a bedroom and the least used. It collects a suitcase, two odd shoes and a layer of dust, when it could hold an entire season of clothing. Under-bed storage bins are the difference between that gap being dead space and being a drawer you had all along.
Done properly it takes an afternoon. Here is the order that works.

These cover everything from a flat slide-under tray to a wardrobe-sized bag, and all sit within the same storage bins and containers range.
The only structured option here. A metal frame means the bin keeps its shape when it is half empty, so it slides out rather than folding in on itself, and the contents do not compress into a single mass. Best for anything you open often.
Three-piece fabric set with a lid, which suits a seasonal swap where the bin is packed once and left. Folds down to nothing between uses, so the bins are not taking up space while empty.
Bags rather than boxes, so they take the shape of the gap. Extra large means whole duvets and winter coats rather than folded shirts. The zip is the thing to check on a bag this size, because it does all the work.
A single bag for anyone with one specific problem to solve: the coats that come out in November and go back in March. Simpler than a multi-piece set and easier to lift when full.
Durable non-woven with a proper lid, which matters under a bed more than anywhere else in the house because that is where dust settles. A lidded box is the option to pick for anything you want clean when you open it in six months.
A double zip opens the box from either end, so you can get at what is inside without dragging the whole thing out from under the bed. Worth the small premium over a single zip if the bin lives somewhere awkward.
Bagged storage compresses and boxed storage does not. If the clearance is tight, a bag will fit where a box will not, but the bag will also let the pile slump when you pull it. Pick by how often you open it rather than by how much it holds.
Leave one bin half empty. The whole system fails the first week you have nowhere to put something, and a spare bin absorbs that rather than the floor.
Put the bins on the side of the bed you actually walk past. Storage you have to crawl over the bed to reach gets used once. This is also the point where a second under-bed organizer on the far side earns its place, because two reachable bins beat one enormous one.
Measure before you buy, keep the heavy things in small bins, and put a lid on anything you want clean later. The framed organizer suits what you open weekly, the bags suit seasonal storage, and a lidded box covers everything in between.
All six are listed on Temu, so you can check the dimensions against your own clearance before ordering.
For the rest of the house, OrganizeTrip goes room by room in far more depth than one article allows.