Answer:
An esbat is the observance of the Moon Ritual - there are several: Full moon, Dark moon, New moon and Blue moon.
Generally they follow a set, basic formula as set out below.
Cleansing - of self and space - a bath or smudging for yourself; sweeping, smudging, asperging for the space.
Creating Sacred Space - calling a sacred circle with an athame, sword, a wand and always with your will.
Invoking the elements - calling the four (or five) elements to witness and/or participate.
Inviting the Deities - For esbats this is usually (but not always) done as a "charge of the goddess".
Working - This is where you you do what spells, rites, etc you have planned. For new moons - beginnings; for dark moons - banishing; for full moons - completions and/or thanks; for blue moons - something special, this year I will be charging blue moon talismans.
Small feast - also known as cakes and ale, this is a small libation and nibble to be shared with all participants and the Deities.
Acknowledgment of the Deities - we NEVER say thanks and dismiss the deities, it would be presumptuous - we say "You have consented to join us and for that we are truly grateful. Go if you must, stay if you will, blessed be"
Devocation of the elements - Thanks and dismissal of the elements (you may command elementals as they are lesser beings).
Dissolution of sacred space - ground the energies and open the circle.