Learn French: Le chien est là.

Chien (dog) is a masculine noun in French. Because it is masculine, we use the masculine word for 'the', which is le. If the noun were feminine, we would use la.

Why doesn't le change to l' here?

We only drop the 'e' and use l' when the following word starts with a vowel or a silent 'h'. Since chien starts with a consonant (c), le stays exactly as it is.

Why does là have an accent mark pointing downwards?

That grave accent marks the difference between là (there) and la (the feminine word for 'the'). They are pronounced exactly the same way, so the accent is just there to help you tell them apart in writing.

How do I pronounce est in this sentence?

The letters 's' and 't' are completely silent. It is pronounced just like a short 'eh' sound. Est means 'is' and comes from the verb être (to be).