The word is - éard. In the dictionary it says -

éard - combined form of é rud used pronominally with copula.
(example) Is éard a deir sé (go) - what he says is (that)

and here's the sentence -

Is éard atá sa leabhrán seo, .......

I don't understand what this means here.

Go raibh maith agat a chara.

So in fact what this expression means, is more than simply - what he says. It's far wider than that. That's what I couldn't understand. Could you give me any other examples as I feel that it isn't explained sufficiently in the dictionary?
For example how would I say? -

(A) What I want to say is.....

(B) What I understand (of it) is.....

or - This is what I want to say - This is what I understand (of it)