Card payments clients make online are recorded as = escapeHtml(PAYMENT_METHOD_ONLINE) ?>, so its name stays.
Renaming it renames it on the = escapeHtml(paymentMethodUsageText($m_usage)) ?> that used it.
Which pickers offer it - money in is payments from clients and other income; money out is expenses, recurring expenses, reimbursements and mileage claims. Transfers between accounts offer every method.