It's a grammatical difference that's also there in English. The first "this" この was actually "this picture," as in it was a demonstrative identifier to the noun "え" while the second "this" これ itself was an independent pronoun, so it acts as a noun and isn't attached to anything. simply put, you've got: これ: this (period) and この: this...(followed by the actual noun you're referring to) that also applies to "that" there are 3 forms of both cases and you'd do yourself a huge favor if you learned them all at once to clear things up. independent forms: - これkore: this (something closer than the listener) - それsore: that (something closer to the listener than the speaker) - あれare: that (distant from both speaker and listener) dependent (attached to nouns) form: このkono: this (closer to listener than speaker) そのsono: that (closer to speaker than listener) あのano: that (distant from both speaker and listener) if you're feeling extra curious, there's another form, the "such..." form, which also attaches to nouns and roughly translates to: こんなkonna: (such as this) そんなsonna: (such as that) あんなanna: (you get the point :D)

also, the わ that follows subjects is written as は. Why? good question *shrug*