1. Conchoical fracture surfaces occur when flint (or other amorphous material) is broken naturally or by hand. But thin pieces (like yours) are most likely to be be man-made.
2. Flints are worked (knapped) to make tools (archeological) and dressed to make building stone in some parts of the country (historical).
3. There is a lot of information on archeological flint tools; too much for me to comment on here in general.
However, flint knapping is a skill, and because of the learning process and mistakes, some pieces that were intended to be tools were discarded; they can be very similar to finished tools, though not as refined.
4. Sometimes, when flints have been dressed into building stone, the small waste pieces are inserted into the pointing (mortar) for decoration or strength; that is called galletting.