What are learning disabilities?
Learning disabilities are disorders that affect the ability to:

Understand or use spoken or written language
Do mathematical calculations
Coordinate movements
Direct attention
Learning disabilities occur in very young children, yet they are usually not noticed until the child reaches school age. Learning disabilities can be lifelong conditions. In some people, several overlapping learning disabilities may occur. Other people may have a single, isolated learning problem that has little impact on their lives.

What is an LD? An introduction to learning disabilities
https://www.youtube.com/watch?v=PR99gf1OwBE

The most common treatment for learning disabilities is special education. Specially trained teachers may perform a formal assessment to understand the child's academic and intellectual potential. They will also look at the level of academic performance. Once the evaluation is complete, the basic approach is to teach learning skills by building on the child's abilities and strengths while correcting disabilities and weaknesses. Other professionals such as speech and language therapists also may help. Some medications may help the child learn by enhancing attention and concentration. Psychological therapies may also be used.
Support for people with a learning disability and family carers
Doctors and other health workers might be able to tell if a person has a learning disability when they are very young. But some people get a diagnosis later in their lives. This can be when they are adults.

If you are diagnosed with a learning disability, you might be referred to other health professionals to get the support you need.

What causes a learning disability?
We do not always know why a person has a learning disability. Sometimes it is because a person's brain development is affected, either before they are born, during their birth or in early childhood.

This can be caused by things such as:
the mother becoming ill in pregnancy
problems during the birth that stop enough oxygen getting to the brain
the unborn baby having some genes passed on from its parents that make having a learning disability more likely
illness, such as meningitis, or injury in early childhood
There are some health conditions where you may be more likely to have a learning disability.
For example, everyone with Down's syndrome has some level of learning disability, and so do many people with cerebral palsy.

references:
https://www.ninds.nih.gov/health-information/disorders/learning-disabilities
https://www.nhs.uk/conditions/learning-disabilities/