Using a pop shield on your microphone is usually used for cutting down unwanted sounds in your vocals. Basically how it works, the pop shield cuts down a bit of treble, this bit of treble can  sometimes create unwanted, irritating sounds in letters such as P or S. When using the pop shield those sounds are less prominent.

A pop shield will also keep your microphone clean when you share your mic with other people.
When using your microphone outside a pop shield will keep the wind out of the mic. Wind can cause some irritating sounds as well when amplified by a mic.

In case you cannot find a pop shield you can also use an old sock. Any type of cloth you can put over the microphone will do the job.

Hope to catch you soon again,
Eddie