"The breakfast is on the plate."
Translation:Tá an bricfeasta ar an bpláta.
After many prepositions (ar, ag, ó, for example) and the singular definite article an, the noun is eclipsed.
ar an bpláta, ag an mbord, ón gcathair, srl
Yes, the p sound is eclipsed by b. bpláta is pronounced as though it was spelled bláta. (mbord is pronounced as though it was mord, gcathair as gathair, etc)
The process is called "eclipsis", and the b in this example is called an urú, which is also the word used to describe a solar eclipse - urú na gréine.