TradeGecko's Payment Method is mapped with WooCommerce Payment Gateway. It is not case-sensitive, and dashes/underscores will be replaced by spaces for matching.
For example, if the Payment Method in TradeGecko is "Credit Card", a Payment Gateway of "credit-card" or "credit card" or "Credit Card" would still match.
This becomes relevant when you have Accounting integration (Xero/QBO). If you do not map Payment Methods accordingly, the Invoice Payment Type will be empty.
And the Invoice will sync to XERO/QuickBooks with its Default Payment Ledger account.