Pus does often mean an infection.
Having pus is a very strong indication of an infection which is often caused by bacteria or fungi or even viruses.
Pus is a byproduct of your body's immune system fighting off an infection.
The puss often appears as a thick, milky fluid that is often white but can also be yellow or green.
The pus itself is not an infection but is a sign of an infection being present and the body is actively fighting off that infection.
Infections can cause wounds which grow and damage more and more surrounding tissue.
The pus is a thick fluid that also contains dead tissue, cells and bacteria and your body produces the pus when it's fighting off an infection.
When you have an infection the pus is a good sign that your body's defense system has kicked in and is working to fight the infection off.
Bacterial infections like the ones caused by staphylococcus bacteria are the most common and frequent cause of pus formation although other conditions such as viral, fungal and even parasitic infections can also trigger the production of pus.
In some cases you may need antibiotics or antifungals or draining of the pus depending on where the pus and infection is and the cause of the infection.