"Envoie-moi un texto s'il te plaît."
Translation:Send me a text message please.
In French the "-o" is a diminutive suffix, many times used to shorten the original word. Like "frigo" instead of "réfrigérateur" , "ado" instead of "adolescent", and "McDo" instead of "McDonalds".
So, in general, the -o suffix is often used to make a normal word sound more slangy/trendy.
"Texto" appears to be the word that caught on to refer to text messaging when it first appeared in France in the early 90s. SFR, a French mobile phone company that has been around since the 80s, tried to copyright the word "Texto", but the courts said the word was in broad use before the trademark filing.
The noun "texte" in French still refers to the classic English definition of "text": a set of written words, but "un texto" and "un sms" are the terms used to describe the modern means of communication.