Aminoglycosides are antibiotics used for gram negative infections. Gram-negative means that the bacteria which cause the infection don't hold the color of a particular dye (Crystal Violet) when they're tested.
Since they are not absorbed from the gut, they are usually taken by an injection into the vain or muscle but they can be given as a cream or ointment to prevent and treat skin infections, as eye drops for eye infections, as ear drops for ear infections and as a pill for intestinal infections but not for other internal infections.
Antibiotics from this family can be used in patients who are not able to take some regular antibiotics, such as Penicillin because of allergies. The most common Aminoglycosides used as alternatives to Penicillin are Erythromycin (lit. Red fungus) and Clarithromycin (lit. Yellow fungus). They're most commonly used in the treatment of bacterial infections, such as Bronchitis.