This sign gives a stopping or silent sound for the letter it comes upon, and it attaches the letter to the very next one. When you say Window, in Arabic rules, here the ‘n’ gets a sukoon (jazm) and it attaches to the letter ‘d’.

Shadda causes the letter it comes upon to be read in double tone, the first sound with a sukoon (stopping) and the second with a Harakat that is also comes with a Shadda (Damma, Kasrah, Fatha).

For example: when we type the word; اِنّ it actually spelled as this اِنْ نَ and it is pronounced as Innominate example when we say Allah, in Arabic form the letter L has ‘Shadda and Fatha’ at the same time so we read in this manner.

Tanween gives an “an, in, un” sound to the last letter of the Word that it comes upon. When Tanween comes in the shape of  double Kasra it reads “in”  as in (begin), when it comes in double fatha it reads “an” as in “can, man”, when it comes in double Damma shape it reads as  “oon” just like pronunciation of “moon” in Arabic form we would see the letter ‘m’ gets double Damma above and it reads in this manner.