I am looking for a dataset/API where I can query a product brand and it can give all the products of that brand along with their description.
You can try our product database at Datafiniti. The entire data set is not "open source", but you can run searches and get up to 1000 records per month for free.
For computer related products check out https://icecat.biz/
Datasets / API / Product sheets and images.
It looks like there are a lot of other product categories added also.