A tablet is a solid medicine made from compressed powder, designed to be swallowed, chewed or dissolved, depending on the product.
Some tablets can be split along a scored line to adjust the dose. Others must be swallowed whole because they have a special coating or release the medicine slowly. Crushing those can release the full dose at once.
Several ADHD medicines come as tablets, including some long-acting methylphenidate products that use a special shell to release the medicine across the day. That empty shell can pass through in your stool. That is expected, and the medicine has still been absorbed.
If you find tablets hard to swallow, say so. Other forms, such as capsules that can be opened, may be available.