Glyphs can have different variations created for many reasons.
The most common ones are:

• for a specific context (e.g., case sensitive, where punctuation signs are better aligned when combined with capital letters);
• stylistic variant of a glyph (e.g., swashed alternates);
• localized variants.

In a digital file, the names of these variations are tagged with an Opentype feature code related to their specificity (parenleft.case, A.swsh, Ldot.locl, etc.) so they can be easily processed in applications supporting these features.