Être en train de is a handy French expression that describes an event in progress. It's always followed by an infinitive and is often translated as "to be in the process of" or "to be in the middle of":

Donc, je suis en deuxième année là;

So, I'm in my second year now;

je suis en train de... achever ma formation.

I'm in the process of... completing my training.

Caption 25, 4 Mains pour 1 Piano - Médaillon de Homard

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Là je suis en train de régler les meules pour que

Here I am in the middle of setting the millstones so that

le grain soit correctement écrasé.

the grain is crushed correctly.

Caption 4, Télé Lyon Métropole - Chaillé-les-Marais : Une biscuiterie 100 % familiale

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BANNER PLACEHOLDER

But just as often, être en train de can simply be translated with the present progressive tense ("to be doing," "to be making," etc.):

Donc, en ce moment, on est en train de faire des truffes cacao.

So, right now, we're making cocoa truffles.

Caption 7, Canadian Chocolate Seller - Chocolats

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In French, there is no difference between the present tense and the present progressive tense: on fait can mean both "we make" and "we are making." So the above example could also be written:

Donc, en ce moment, on fait des truffes cacao.
So, right now, we're making cocoa truffles. 

Être en train de emphasizes the fact that the activity is currently in progress (further emphasized above by en ce moment). In fact, "currently" is another possible translation of être en train de:

...je suis en train de travailler avec celui qui a fait 'Pulp Fiction',

...I'm currently working with the person who made 'Pulp Fiction,'

Caption 9, Melissa Mars - From Paris with Love

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You can also use être en train de to describe a continuing event in the past. In this case, it's synonymous with the imperfect tense: 

Quand j'ai fait cette photo, la baleine était en train de dormir.

When I took this picture, the whale was sleeping.

Caption 25, Le Journal - Sillonner & photographier les océans

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Quand j'ai fait cette photo, la baleine dormait.
When I took this picture, the whale was sleeping.

Here again, être en train de stresses the continuousness of the action: the whale was "in the process of" sleeping when the speaker took the picture. 

Être en cours de has the same meaning and function as être en train de, except it's usually followed by a noun instead of an infinitive:

Un immense chantier est en cours d'achèvement.

A huge construction project is being completed.

Caption 25, Voyage dans Paris - Cour de l'Industrie

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BANNER PLACEHOLDER

A final note: Make sure not to confuse en train with entrain, a noun meaning "enthusiasm" or "liveliness." Nous espérons que vous êtes en train d'étudier le français avec entrain! (We hope you're in the process of studying French with enthusiasm!)