"Her father's name is Peter."
Translation:उसके पिता का नाम पीटर है।
Prepositions and postpositions are parts of speech which indicate various relations between nouns and other parts of a sentence.
In English, we use prepositions like 'in', 'for', until', 'from' and so on. These are called prepositions because they come before the noun they are connected to. For example, 'in India', 'for Neha', 'until today'. These nouns (or noun phrases like in 'from my house') that come after the prepositions are called objects of the prepositions.
On the other hand, Hindi uses postpositions which come after the noun they are connected to (ie, their object). For example, 'भारत से', 'नेहा केलिए', 'आज तक', 'मेरे घर से' etc where ' से, केलिए, तक, से are postpositions and 'भारत', 'नेहा', 'आज', 'मेरे घर' are nouns/noun phrases that are their objects.
Such nouns that are objects of postpositions in Hindi are said to be in the 'oblique case' and may have a different form than normal. I have written a bit more about the oblique case here.