Many people in India use the word marriage when referring to the ceremony where a marriage takes place, instead of the more appropriate wedding. However, the use of marriage in this context is not wrong, as is apparent from the second definition of the word shown in this screenshot from the Macmillan dictionary.
Nevertheless, wedding should be the preferred word since it refers specifically to the ceremony.
You can easily remember this distinction if you keep in mind the following film-titles, all of which use wedding rather than marriage.
- My Big Fat Greek Wedding
- My Best Friend's Wedding
- Monsoon Wedding