In Tagalog there is no such thing as the verb to be.
In many Western languages we use the verb “to be” in such sentences as:
“I am Italian”
“I am an office worker”
“I am a husband”
“She is my wife”
“Rodrigo Duterte is the president of the Philippines”
“Mocha Uson is a politician”
And so on
In Tagalog these sentences would literally read:
“Italian I”-Italyano ako
“Office worker I”-Empleyado ako
“Husband I”-Asawang lalaki ako
“My wife she”-Asawa ko siya
“President of the Philippines Rodrigo Duterte”-Presidente ng Pilipinas si Rodrigo Duterte (I have explained how to use the marker si before a personal name in my post about markers in Tagalog)
“Politician Mocha Uson”-Pulitiko si Mocha Uson
The order of all these sentences can be switched by using the marker ay.
So, for example, the expression Italyano ako can be flipped like this: ako ay Italyano
Pulitiko si Mocha Uson can be switched and turned into: si Mocha Uson ay (ang isang) pulitiko
The same kind of switching can be done when using verbs
If, for example, I am using the verb to go in a sentence like pumunta ako sa Pilipinas (I went to the Philippines), I can flip that sentence and say: ako ay pumunta sa Pilipinas
Or, if I say something like nagbabasa ako ng isang aklat (I am reading a book), I can switch it like this: ako ay nagbabasa ng isang aklat
Just remember that ay is just a marker that switches the order of the sentence and has nothing to do with the verb to be, as there is no verb to be in Tagalog.
Ay can also have another meaning: you can hear it in a sentence like ay naku!
In this case ay basically means oh, and the whole expression ay naku! means something like oh my goodness!
I hope this clarifies what ay means in Tagalog.