Often a garage is built with a concrete floor. This can make it very sturdy and strong but is often not the most comfortable and does not offer much warmth. If you want to only use your garage to store your car in or to store tools and gardening equipment then that may be fine but if you want to use the garage like another room such as a playroom, gym or laundry room you may decide to put down different flooring.
If the room is going to be used as a playroom then why not fit some carpet? This will instantly transform the room and make it feel cosy. If you are going to do this you do need to ensure that the garage is waterproof as if not, the carpet will get wet and become mouldy / damp. It is also important to ensure that you have ventilation to allow fresh air to circulate. Many rooms have a ventilation brick, but these often get covered up over time, so ensure that this is left open. For a laundry room you may prefer to have lino which again will be a little warmer but more practical should you have spillages etc.