Logo & Trade Mark Device
A logo is the graphic identifier of a company, typically consisting of a wordmark (the styled name), a symbol, or a combination of the two. Its job is recognition rather than explanation: it must be distinctive, legible at any size and usable for years.
In practice
You need several versions from the outset: a primary lock-up, a horizontal and a compact variant, a single-colour version for stamps and engraving, and a light version for dark backgrounds. The most common mistake is a logo with fine detail or gradients that turns to mush on an engraved pen or in a favicon; test every draft small and in black and white before deciding. Always have the files handed over as vectors (SVG, EPS or AI), not only as PNG. Agree the usage rights in writing, and check before rollout whether a similar sign is already registered as a trade mark.