Under netting, buying 1 lot and then buying another gives you 2 lots at a blended price; selling 1 lot afterwards leaves 1 lot. There is only ever one position per instrument, and the platform shows an average entry rather than a list of entries.
This is the model required for US retail forex accounts under nfa-compliance-rule-2-43 and it is standard in institutional systems. It makes exposure obvious, which is its main advantage over hedging-mode: you cannot be simultaneously long and short and confused about which is which.
Stops and targets attach to the net position, so adding to a trade means revisiting the protective orders rather than letting each entry carry its own.
Example: buy 1 lot at 1.0800 and 1 lot at 1.0900. The netted position is 2 lots at an average of 1.0850. Breakeven is now 1.0850 for the whole thing, not two separate levels.
Related: hedging-mode, fifo-rule, metatrader, used-margin