If you want a phone that has with it a "pure Android" experience, meaning one where there is no carrier and/or manufacturer apps and custom inferfaces, can be easily modified or be used as a developer phone, be the first to receive OS updates, have flagship-level hardware (when it was released), minimalist design, a size that's considered medium in smartphone circles (4.95 inch display), can be used most anywhere in the world (unlocked), then the Nexus 5 is for you.
As of this writing, even with the much larger Nexus 6 released, the Nexus 5 still can compete with a number of the flagship phones in the market, and is a value and size alternative given the price point. With the release of Android 5.0 (Lollipop) OS, the experience is even snappy and smoother than ever.
It's considered one of the best flagship Android smartphones of the latter half of 2013. It carries with it the newest version of Android OS (4.4 KitKat). Hardware includes:
It was released via Google Play as an unlocked device on October 31, 2013, then later to carriers.
Since the question doesn't specify what Nexus the person is comparing it to the Nexus S, here's the order of Nexus phones (and by manufacturer) to date: -HTC Nexus One -Samsung Nexus S -Samsung Galaxy Nexus -LG Nexus 4 -LG Nexus 5
The Nexus 5 comes unlocked, and is compatible with T-Mobile. Simply plug in the micro SIM card and it should be able to run on their network.
Google, with a collaboration with manufacturer LG.
Samsung Galaxy S3, Samsung Galaxy Note 2, HTC Droid DNA, LG Nexus 4, Iphone, LG Nexus 4, Motorola Droid Razr Maxx HD. HTC Sensation, Iphone 4S and the LG Prime.
The Google Play Store and the Amazon Appstore are two good places to find quality apps for your Nexus 5.
I believe the Netgear PTV3000 and the LG DWD-300 are two that work on the Nexus 4.
The LG Nexus 4 came out in November 2012. A white variant came out later, with some minor physical hardware improvements.
It was likely built in South Korea, as LG is based there.
Likely in South Korea, as the manufacturer (LG Electronics) hails from there.
The Nexus 5 was released on October 31, 2013.
Since the Nexus S, Google brought out the Galaxy Nexus, Nexus 4, and Nexus 5.
Both phones are manufactured by LG, and they largely have the same architecture. Some of the differences is the G runs on an LTE network (Nexus 4 is HSPA+), has an expandable microSD slot (Nexus 4 has no expandable slot), has a removable battery (Nexus 4 battery is sealed), a 13 megapixel camera available (Nexus 4 only has a 8 megapixel camera), and runs on Android 4.1 Jelly Bean with a manufacturer skin (Nexus 4 has Android 4.3 Jelly Bean stock).