Incontinence refers to the inability to control when you pass urine (pee) or have a bowel movement (poop). It's commonly used to refer to someone who doesn't have "control" over their bowel or bladder. On it's own, saying someone is incontinent doesn't say enough about how their body eliminates waste, and how that may change in the future.
The major distinction in incontinence is whether someone has bladder or urinary incontinence (and therefore can't fully control when they urinate), or bowel or fecal incontinence (and therefore can't fully control when they defecate). There are many different kinds of incontinence, which may be temporary or permanent. Incontinence may result directly from an illness, disease, or impairment, or from treatment including medication and/or surgeries.
Incontinence in and of itself doesn't necessarily impact sexual function or response, but the factors that lead to incontinence may have an impact on sexual response, as might treatments to deal with incontinence. For many, the larger obstacle to sexual activity and pleasure is related to the social taboos about urine and feces combined with narrow social definitions of sex, which can lead people to feel as if incontinence means the end of partnered sexual activity.