In Drift, user's current position is the cumulative sum of their orders (increasing, reducing, or closing) over time, i.e. all trading lots are combined into a single position.
The position table then shows the Unrealised PnL for the current position. You can select to see in "$" or "%" terms.
Active trading may move funds between Unrealised PnL and Realised PnL.
The most important value is Total Collateral (Collateral + Unrealised PnL)
Currently, only the lesser of Free Collateral and Realised Collateral is available for withdraw. Closing/reducing position will add to realised collateral for withdraws to make additional funds available. In the future, Drift is adding instruction to convientantly settle Unrealised PnL without trading.
(For time being, another suggestion for a user who wants to 1) stay in a position. and 2) withdraw unrealised profits in excess of their realised collateral. is to close and reopen the position) Read more in Trading Glossary