This is a dua which is repeatedly invoked when Muslims go for pilgrimage. It’s also referred to as Talbiyah.
Talbiyah is repeatedly said during the Hajj, or pilgrimage, or upon putting on the Ihram.
Reciting the full labaik allahuma labaik is form of remembrance of Allah (swt), it’s a realization that He alone is the source for all blessings.

لَبَّيْكَ ٱللَّٰهُمَّ لَبَّيْكَ، لَبَّيْكَ لَا شَرِيكَ لَكَ لَبَّيْكَ، إِنَّ ٱلْحَمْدَ وَٱلنِّعْمَةَ لَكَ وَٱلْمُلْكَ لَا شَرِيكَ لَكَ

Labbaik Allahumma labbaik. Labbaik la sharika laka labbaik. Innal-hamda wa-nimata laka wal-mulk, la sharika laka.

I respond to Your call O Allah! I respond to Your call. You have no partner. I respond to Your call. All praise, thanks and blessings are for You. All sovereignty is for You. And You have no partners with You.

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