Lower back pain is common affecting about 80% of people at some point in their lives. Acute back pain resolves within 6 weeks but chronic back pain, by definition, lasts longer. Sciatica implies entrapment of the sciatic nerve into the leg causing numbness and/or pain and in more severe cases weakness.
The following weblink is useful for back pain
https://www.nhs.uk/conditions/back-pain/
The following weblink is useful for sciatica
https://www.nhs.uk/conditions/sciatica/
Arthritis research UK has some useful advice on back exercises
For those who would like to give joga a try to address their chronic back or sciatica there is a wealth of online self help videos on youtube. I suggest these as an introduction.
https://www.youtube.com/watch?v=G5h0jkoBFbI
https://www.youtube.com/watch?v=XeXz8fIZDCE