The following is a short list of main attributes of Chrono.

Physics modeling

Rigid body support
Flexible body support via Chrono::FEA module - both for ANCF and co-rotational nonlinear finite element analysis
Support for fluid-solid interaction problems, via Chrono::FSI module
Coulomb friction model capturing stick-slip phenomena.
Support for rolling friction and spinning friction.
Support for handling frictional contact via two approaches: a complementarity approach and a penalty approach.
Springs and dampers with non-linear response. Can be user defined.
Large collection of joints and constraints: spherical, revolute, prismatic, universal, glyph, screw, bevel and spur gears, pulleys, etc.
Unilateral constraints.
Constraints to impose trajectories, or to force motion on splines, curves, surfaces, etc.
Constraints can have limits (ex. elbow).
Constraints can be rheonomic or holonomic
Custom constraint for linear motors.
Custom constraint for pneumatic cylinders.
Custom constraint for motors, with reducers, learning mode, etc.
On the fly constraint activation/deactivation.
Simplified 1D dynamic models. Examples: powertrain, clutches, brakes, etc. For more sophisticated models see companion Chrono::Vehicle module.
All physical items can have an arbitrary number of 'assets' used for defining visualization shapes, custom properties, etc.

Solver

HHT solver for index 3 differential algebraic equations.
Symplectic first order half-implicit Euler solver for large frictional contact problems.
Speed-impulse level solver for handling large frictional contact problems.
Handling of redundant/ill posed constraints.
Stabilization or projection methods to avoid constraint drifting.
Static analysis solver.
Inverse kinematics and interactive manipulation.

Supports compounds of spheres, cubes, convex geometries, triangle meshes, etc.
Additional collision support provided by the Bullet collision detection engine, which is wrapped inside Chrono::Engine.
Broad phase collision detection: sweep-and-prune SAT.
Narrow phase collision detection: AABB and/or OBB binary volume trees, to handle geometries with thousands of details.
Detail phase with custom primitive-to-primitive fallbacks.
Safety 'envelope' around objects.
Report penetration depth, distance, etc.
Bodies can be activated/deactivated, and can selectively enter collision detection.

C++ syntax (requires C++11)
Optimized custom classes for vectors, quaternions, matrices.
Optimized custom classes for coordinate systems and coordinate transformations, featuring a custom compact algebra via operator overloading.
All operations on points/speeds/accelerations are based on quaternion algebra and have been profiled for fastest execution.
Custom sparse matrix class.
Custom redirectable stream classes, featuring platform independent file archiving and modern syntax.
Special archive engine, with easy and reliable persistent/transient serialization. Includes versioning and deep pointers storage.
Expandable run-time class factory.
Custom pseudo-'run-time-type-information', to allow persistence even in case of name-mangling with different C++ compilers.
High resolution timer, platform independent.