If this option is unchecked on Customize > Leads > Settings, ‘Enforce Validation and Triggers from Lead Convert’ then the validation rules and triggers of account, contact & opportunity are bypassed but the validation rules and triggers of lead execute.
What is the difference between Apex Data Loader and Import Wizard as far as generating extra accounts is concerned?
If a submitted record meets entry criteria of multiple approval processes, then which approval process will it enter?
Lead validation rule (like field Industry must have a value) always triggers when a lead is converted.