Muscle fibers are combined into bundles of sorts
like these☝🏻
These muscle bundles are enclosed in a special sheath, the perimysium. A group of bundles are united in another connective tissue sheath, the epimysium.
Why does a muscle need such a complex system?
Thanks to the bundles, the muscle can have a unique structure, because the bundles can go in different directions. Accordingly, perform different functions.
As an example, the calf muscle has a pinnate structure - it provides a large force, but a small amplitude and speed of movement.
But the arm flexors have a spindle-shaped structure - the body sacrifices strength in favor of speed and amplitude.