There are a lot of programs and applications that can influence your broadband speeds.
Backup programs such as Apple iCloud and Dropbox will work in the background of your PC or devices to back up to a cloud based services and depending on its configuration, can severely degrade your connection if it starts to use up your available upload bandwidth.
Streaming programs and Apps such as Netflix on your Smart TV can also affect your speeds, especially if you start watching and streaming high definition TV, normally a single streaming movie or show should not slow you down however if multiple shows or movies are being watched at the same time, your connection may slow down due to everyone potentially using most of your available download bandwidth.
Other programs such as VPN Clients (Virtual Private Networks) will also have an effect as your data would be going through a different route, typically this more common if you work from home with a work provided PC or Laptop.
Another type of program that will also affect your connection will be Peer to Peer programs (P2P), these typically run in the background continuously uploading and download data and when configuring poorly can cause your connection to barely deliver any other internet service.