A bud is meristematic tissue which occurs on the tip of a branch or at a stem node at the axil of a leaf where it will develop into a new shoot or flower. Whether it produces a shoot and/or a flower determines if it is a vegetative bud (produces leaves and shoots), a flower bud (produces a flower), or a mixed bud (produces both shoots and flowers).
Buds are also named based on where they occur on the plant. If a bud occurs on the tip of a stem, then it is called a terminal or apical bud. Lateral buds are those which occur on the side of stems. Those lateral buds that occur at the leaf axil where the leaf attaches to the stem are called axillary buds. Buds can also occur beside axillary buds and at the base of terminal buds, and when this occurs, those additional buds are called accessory buds.
Latent or dormant buds remain concealed on internodes beneath the bark until a branch breaks or is cut off just above it in which case the latent bud may develop a new shoot to replace the wood that has been removed.
Adventitious buds develop in unusual places other than the apical meristem. They can develop on roots, the callus edge of shoots that have been damaged or pruned, or the epidermis of leaves. They can develop on mature tree trunks that were previously shaded but exposed to sunlight because the trees around it were cut down.
When deciduous plants lose their leaves in the fall, leaf scars are often visible where the leaves used to attach to the stem below their axillary buds. When leaves fall from the tree, leaf scars develop a thin layer of cork to protect the plant from fungi and water loss. Often you can see small dots in the leaf scar called leaf traces or vascular bundle scars where vascular bundles transported water, nutrients, and food between the leaf and the stem.