It's a term of pity or sympathy, usually used for a female person or animal that is perceived as being unfortunate or experiencing hardship.
Here's a breakdown of the meaning:
* Pobre: poor, unfortunate
* -cita: diminutive suffix, making the word more endearing and emphasizing the feeling of pity
For example, you might say "Pobrecita, se cayó y se lastimó" (Poor thing, she fell and got hurt).