To fully break it down.
Level 2 Magus has one attack when taking a full attack action.
Thus with Spell Combat, he casts a spell and gets one attack (or vice versa; attack then spell).
If any character casts a touch spell, he gets a free action touch attack to deliver that spell within the same round. Spellstrike allows you to replace that touch attack (which any character has) with a weapon attack. Thus you would get two weapon attacks (one with the spell as a rider), instead of one weapon attack and one touch attack.
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Spellstrike doesn't grant any attacks. It just lets you use a weapon to deliver touch attacks that you already could make.
To understand Spell Combat and Spellstrike, I highly recommend Grick's Guide to Touch Spells, Spellstrike, and Spell Combat.
Edit: 9 second ninja'd by Brevick Axeflail. :)