I do all my gardening in raised beds. I use 2×6′s to define my garden. It is best not to use pressure-treated wood. The advantage of raised beds is it clearly defines the garden. I never step on the soil in the beds. All my raised beds are 4×5 ft. or 4×4 ft. in dimension. This allows me to reach any part of the garden without stepping on the soil.
Raised beds allow you to only water or fertilize the part of the garden that you are using. By using a raised bed you plant more of the garden which shades the ground and helps prevents weeds from growing. And because the soil is so loose, weeds pull out a lot easier.
Another advantage is to the new gardener. Many new gardeners will loosen the soil in their fame and then use good trucked-in soil. This is a shortcut to spending 5 years developing good soil.
By building the soil up above ground level, the raised bed allows for better drainage. While the soil in the paths is hard and compact The soil is like a basin full of loose dirt where the rainwater pools in the bottom for when the plant needs it.
Around my raised beds I like to use wood chips. This help to keep the weeds down and keeps me from getting muddy shoes. Any mud or dirt that does get in the paths quickly works its way through the chips.