I do not understand the concept of environmental feedbacks. Could you help explain it to me using examples?

First of all, you need to understand the difference between positive and negative feedbacks, we can then work on examples. A feedback starts with an initial perturbation/disturbance, in the case of a positive feedback the scale of the initial perturbation is amplified. On the other hand, negative feedbacks suppress the initial perturbation. 

Now for some examples. Firstly, a relatively easy positive feedback to understand relates to the ice albedo and its effect on atmospheric warming. An initial heating of the earths atmosphere could be caused by a number of natural or human phenomena (how many can you/we name?). This initial heating causes ice to melt reducing ice surface area and therefore the albedo of the earths surface. The average reflection coefficient or albedo of ice with snow is 0.9 so it reflects 90% of incoming radiation, the average albedo of open water is 0.06 so it absorbs 94% of incoming radiation (www.us-satellite.net). For this reason as ice melts, more radiation is absorbed, causing further ice melt and therefore further reduced albedo and enhanced warming.

A good example of a negative feedback is when an initial warming causes higher amounts of evaporation from water bodies such as oceans. This increases the amount of water vapour in the air and therefore clouds so can cause the initial warming perturbation to be reduced as clouds have a high albedo and reflect incoming solar radiation.