1. the most relevant information about something
give someone the low-down about how something works
As an adjective 'low down' refers to something mean and unfair. "His low down behaviour doesn't reflect well on the organisation." "Her low down tricks have made her look bad in front of the managers." As a noun, 'the lowdown' refers to real facts or true information about something. "Daniel is new to the company, could you walk him through the office and give him the lowdown on what's going on?" "Our newspaper promises to give you the lowdown on all of our politicians each week." This is an informal expression used in both social and professional contexts.