The meaning of Attahiyat:
All the compliments, prayers, and pure words are due to Allah.
Peace be upon you, O Prophet, and the mercy of Allah and his blessings.
Peace be upon us and upon the righteous slaves of Allah.
I bear witness that none has the right to be worshipped except Allah and I bear witness that Muhammad is His slave and Messenger.
Attahiyat full dua Arabic
التَّحِيَّاتُ لِلَّهِ وَالصَّلَوَاتُ وَالطَّيِّبَاتُ السَّلاَمُ عَلَيْكَ أَيُّهَا النَّبِيُّ وَرَحْمَةُ اللَّهِ وَبَرَكَاتُهُ السَّلاَمُ عَلَيْنَا وَعَلَى عِبَادِ اللَّهِ الصَّالِحِينَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ
Attahiyat dua in English
At tahiyyātu lillāhi was salawātu wat tayyibāt, as salāmu ‘alaika ayyuhan nabiyyu wa rahmatullāhi wa barakātuh. As salāmu ‘alainā wa ‘alā ‘ibādillāhis sālihīn, ash hadu al lā ilāha illal lāhu wa ash hadu anna Muhammadan ‘abduhū wa rasūluh.
-Sunan an-Nasa’i 1164, Sahih Muslim 403