French kissing is an old term used for kissing with tongues. This is a very intimate type of kissing and is used as foreplay. Not all escorts offer French kissing. Some escorts will say they are happy to kiss with no tongues. It is common for escorts who have partners in their real life to not offer French kissing as one of their services. French kissing escorts often also offer the full GFE (Girlfriend Experience).
French kissing is normally associated with passion and love, French kissing can be very arousing and often leads to more intimate sexual activities. French kissing is a great way to warm up at the start of the appointment, explore what each other like before moving forward and find out if your partner enjoys soft French kissing or hard and passionate French kissing.
When booking an escort, if you ask if they kiss, clarify with them they are happy to French kiss with tongues, otherwise, this could be misconstrued and you may be visited by an escort who only offers closed-mouth kissing, which is not as arousing and erotic as it would be if you could use your tongue.