Your normal temperature is around 98.6ºF (37ºC). When your body gets hotter than this temperature, the hypothalamus (a part of your brain) tells your body to lower that temperature and tells your sweat glands to perspire.
Perspiration doesn’t actually have a smell, but the bacteria on your skin are the stink culprits. And then there is puberty, a time when glands in your armpits and groin become active.
There are two types of sweat glands. The eccrine glands are active throughout life. The apocrine become active in puberty. Located in hair follicles, they produce sweat that contains fatty acids and proteins. The bacteria processing the fatty acids and protein cause the body odor that requires deodorant.
With temperatures in the 90s and up in the Northern Hemisphere, you might be doing a little sweating. Here is an interesting infographic from the Cleveland Clinic on sweat.