From the Super Mario Wiki
in New Super Mario Bros. 2
A Wooden Block is a type of block that is found in Super Mario Bros. 3 that cannot be destroyed. Some Wooden Blocks may contain an item, but they will not turn into a Used Block after being hit. Wooden Blocks will only ever yield items if they are hit from the side, and not from underneath. Mario or Luigi need only to press against the side of a Wooden Block containing an item in order to reveal it, as opposed to having to use a Shell or a Raccoon tail like with other types of blocks. In Super Mario Bros. 3, Chain Chomps are attached to these.
These blocks were originally going to return in Super Mario World, but didn't make it to the final game. There are two Rotating Blocks that act like the ones that yield items, and one only yields Cape Feathers while the other one does nothing (presumably, this one is what the Feather block would become once it released its Feather).
Wooden Blocks return in the Nintendo 3DS game Super Mario 3D Land, where they are bigger and more yellow than the ones in Super Mario Bros. 3.
Wooden Blocks appeared in New Super Mario Bros. 2, and looked similar to their first appearance version. They are used as solid and stationary platforms.
Colorful Wooden Blocks reappear in the Wii U game New Super Mario Bros. U, where once again act as platforms.