Sometimes it is hard to define these without using the same words…
Deep research models are designed for tasks that require collecting and analyzing a lot of information from a lot of sources. This can include facts, opinions, official documents, anecdotes, etc. (You know, research…)
These models will gather a lot more information than other models and put it all together to draw conclusions and answer your questions.
These are becoming more popular, and most of the larger AI chatbots now have deep research models available - ChatGPT, Gemini, Perplexity, Claude, etc.
There are a lot of different groups of research - i.e., medical, legal, financial, business, etc.
If you have research projects, AI tools can be a low-cost and fast research assistant.