T Series (2000–current)

The T Series historically had high-end features, such as magnesium alloy rollcages, high-density IPS screens known as FlexView (discontinued after the T60 series), 7-row keyboards, screen latches, the Lenovo UltraBay, and ThinkLight. Models included both 14.1-inch and 15.4-inch displays available in 4:3 and 16:10 aspect ratios.

Since 2012, the entire ThinkPad line was given a complete overhaul, with modifications such as the removal of separate buttons for use with the TrackPoint (**40 series - 2014, then reintroduced **50 series - 2015), removal of separate audio control buttons, removal of screen latch, and the removal of LED indicator lights. Models starting from the **40 series featured a Power Bridge battery system, which had a combination of a lower capacity built-in battery and a higher capacity external battery, enabling the user to switch the external without putting the computer into hibernation. However, beginning with the 2019 **90 series models, the external battery was removed in favor of a single internal battery. Also, non-widescreen displays are no longer available, with 16:9 aspect ratio as the only remaining choice.

The most famous T-Series ThinkPad is the Tx20 Series of ThinkPad. The Laptops came in two editions: 15"(T520) or a 14"(T420). These ThinkPads are widely known to be the last ThinkPads to use the classic 7-row keyboard. Even though Enterprises and Governments have mostly phased out this 2011 ThinkPad, this is still one of the most popular models with I.T users (T-Series or Otherwise.) The Tx20 line of laptops is also known for its outstanding Linux compatibility.

Over time, The T-Series ThinkPad's purpose has changed. Initially, the T-Series ThinkPad was meant to have high-end business features and carry a 10-20 percent markup over the other ThinkPads. Starting with the T400, The ThinkPad T-Series became a less of a high-end business laptop and became more suited as a mobile workstation, becoming similar to the W-Series or P-Series ThinkPads. Achieving similar performance to the W-Series, but with a 5-10 percent smaller profile than the W-Series ThinkPads. In 2013, the T440 introduced another major shift in The ThinkPad T-Series. The ThinkPad became more of an overall office machine than a mobile workstation. By today's standards, The ThinkPad T-Series is thicker than most of its competitors.

Source: Wikipedia