Blockages can be causing be all manner of issues, whilst Fats, Oils and Grease, wipes, sanitary products and a whole host of other crud should never be put down the sewer, a lot still is, and thousands of tonnes of this detritus is removed from sewers and/or sewage every week at some point.
Other issues can be dropped joints, collapsed pipes, belly (dip) in the pipe, blocked Interceptors, etc etc. Best advice for anyone who is unsure, first off speak to your Water Company, if it's a shared drain, they are responsible. If not, then seek a recommendation for someone who knows what they're doing, before you hurt yourself or someone else.