what was the campaign about?
The United States wanted to neutralize the major Japanese base at Rabaul while also supporting the Allied New Guinea campaign.
Actions along the Matanikau
On 7 August 1942, Allied forces (primarily American) landed on Guadalcanal, Tulagi, and Florida Islands in the Solomon Islands. The landings on the islands were meant to deny their use by the Japanese as bases for threatening the supply routes between the U.S. and Australia, and secure the islands as starting points for a campaign with the eventual goal of neutralizing the major Japanese base at Rabaul while also supporting the Allied New Guinea campaign. 
what is 'actions along the matanikau'? Two engagements between forces during the Guadalcanal campaign. who were the two forces? United State and forces of Imperial Japan.
wiki:8595806
Actions along the Matanikau [SEP] Background
On 7 August 1942, Allied forces (primarily American) landed on Guadalcanal, Tulagi, and Florida Islands in the Solomon Islands. The landings on the islands were meant to deny their use by the Japanese as bases for threatening the supply routes between the U.S. and Australia, and secure the islands as starting points for a campaign with the eventual goal of neutralizing the major Japanese base at Rabaul while also supporting the Allied New Guinea campaign. The landings initiated the six-month-long Guadalcanal Campaign. Taking the Japanese by surprise, by nightfall on 8 August the Allied landing forces had secured Tulagi and nearby small islands, as well as an airfield, later called Henderson Field by Allied forces, under construction at Lunga Point on Guadalcanal.