The M141 is a very different weapon from the Javelin, an advanced guided anti-tank missile that has become a hallmark of U.S. military
The Bunker Defeat Munition (BDM) is a disposable single-shot launcher preloaded with an unguided 83mm rocket-propelled projectile designed to engage targets at relatively short ranges.
Development of what was originally known as the Shoulder-Launched Multipurpose Assault Weapon-Disposable (SMAW-D) started in the 1990s in response to requirements from the U.S. Army. The service was primarily looking for a weapon that would give small units an additional tool for dealing with enemy fortifications on the battlefield, such as pillbox-type concrete bunkers and earthen berms.

McDonnell Douglas initially lead the project, before that company merged with Boeing in 1997. Talley Defense Systems, now a U.S.-based division of Norwegian defense contractor Nammo, subsequently acquired the design. The SMAW-D beat out a competing design based on the Swedish AT-4, a disposable single-shot anti-tank weapon that is also in Army inventory. The service took the first deliveries of what it subsequently designated the M141 in 1999.
M141 is derived from Mk 153 Shoulder-Launched Multipurpose Assault Weapon (SMAW), a reloadable shoulder-fired weapon that McDonnell Douglas developed from the Israeli-designed B-300 for the U.S. Marine Corps in the 1980s. The BDM fires a so-called high-explosive dual-purpose (HEDP) round that is similar to the one available for the SMAW, but with a redesigned rocket motor that reduces its range. The M141 has an effective firing range of up to 250 meters, while the latest versions of the SMAW can reliably engage threats out to 500 meters.

Overall, the BDM is more akin to the most modern variants of the venerable M72 Light Anti-Tank Weapon (LAW), a disposable, single-shot, shoulder-fired launcher pre-loaded with one of a number of types of rockets, including an anti-structure type. For added context, the most recent versions of the shoulder-fired Javelin missile have an effective range of up to 4,000 meters.
For instance, in the early phases of U.S. operations in Afghanistan following the 9/11 terrorist attacks, American troops used BDMs to collapse caves that Taliban militants and Al Qaeda terrorists were using as fighting positions.
BDMs can be used to blast holes in walls and otherwise breach obstacles, creating alternate pathways around the battlefield for friendly forces, as well. These weapons also have a secondary capability against light armored and unarmored vehicles and could be used to destroy caches of ammunition, fuel, and other similar materiel.

It is important to note that this weapon does have a significant backblast while firing, which precludes it from being employed from inside confined spaces, such as a room inside a building, forcing the user to expose themselves at least to some degree.
Beyond their utility against various different target sets, the M141s have the benefit of being easier to train personnel to use compared to more complex guided missile systems, such as Javelin. This relative ease of use also opens up the possibility of distributing them on a wider basis and utilizing them, where appropriate, in lieu of missiles, helping to preserve stocks of those weapons for higher-priority targets.
While the BDM is in no way a substitute for anti-tank guided missiles, they are still very much multi-purpose weapons that could give even small continents of Ukrainian troops additional capabilities and capacity to engage a variety of targets in any future conflict.