Even I get it wrong on Syria sometimes (quite often)
As you can see from the map, there are areas that are disputed between the government and ISIL. There has been one recent offensive by government forces towards ISIL territory, about 30 km east of Aleppo (north towards Al-Bab). By contrast, there have been 3 recent offensives from government territory south of Aleppo, north-west, west and south-west, onto the area controlled by the "rebels" (FSA & others).
From rebel-controlled East Aleppo, there is a narrow exit from near-encirclement by government forces and then a narrow corridor to the Turkish border. There have been 2 recent offensives on this corridor: westwards by ISIL; and eastwards by the SDF (this is presumably the capture of the village of Tanab, advancing towards A'zaz, that I mentioned previously). The FSA have attacked out of this corridor, eastwards into ISIL territory, just south of the Turkish border.
The YPG have said that their first priority is to link the Kurdish enclave of Afrin in the west with Kobane to the east, clearing the remaining 60 miles of the Syria–Turkey border from ISIL control. To roll back ISIL is clearly understandable and unproblematic (except for Turkey). But to link up Afrin to Kobane, the SDF would need to cross or control the stretch of border currently controlled by the FSA (which is obviously their supply route to Turkey). This is not mentioned in the Wikipedia article, nor in Roy Gutman's report for McClatchy on which it is based "U.S. begins airdrops of weapons to Kurdish forces in northern Syria", 12 October 2015).
Without wanting to make excuses, I think my errors are indicative of one thing: that the Syrian conflict is not always covered in sufficient depth by the "mainstream media". I don't always have the time to dig out the truth from obscure Tweets.
Update: this is from Reuters' report, 1 Jan:
A U.S.-backed alliance of Syrian Kurdish and Arab fighters advanced against Islamist insurgents in the north of the country on Friday, capturing at least one village in Aleppo province [..] Fighters from the Democratic Forces of Syria seized the village of Tanab near the town of Azaz after heavy clashes with the al Qaeda-linked Nusra Front and the powerful Ahrar al Sham, spokesman Talal Selo told Reuters. "We liberated Tanab," he said.[.. T]he Syrian Observatory for Human Rights said the Democratic Forces of Syria had also captured the village of Tat Mrash. Selo said he could not yet confirm its capture....
The alliance has separately [from its fight against ISIL] been fighting in recent weeks against Nusra Front, Ahrar al Sham and other insurgents in northern Aleppo province. .The Democratic Forces of Syria includes the Kurdish YPG militia, which has been the most effective partner on the ground for U.S.-led air strikes.